Split out linearfb from efifb so that boot loaders can program it as asimple linear framebuffer on non-EFI systems. This is useful for bootloaders with their own graphics drivers, e.g. GRUB 2, since in somecases on x86 they can set up non-VESA modes and thus can't programvesafb.

efifb is reworked on top of this common code, and it should be possibleto do the same with some other framebuffer drivers in future.